Process for cold forming metal



R. H. ANDERSON ETAL 3,367,216

PROCESS FOR COLD FORMING METAL Feb. 6, 1968 Filed June 30, 1966 ROY H. ANDERSON DOUGLAS J. LE RY INVEN R.

ATTORNEYS V United States Patent Ofllice 3,367,215 Patented Feb. 6, 1968 3,367,216 PROCESS FOR COLD FORMING METAL Roy H. Anderson and Douglas J. Lemery, Victoria, British Columbia, Canada, assignors to Atlas Chain Co., Ltd., Victoria, British Columbia, Canada Filed .June 30, 1966, Ser. No. 561,935 8 Claims. (Cl. 76112) The present invention relates to a method of forming or fabricating shapes from precision fiat strip stock which may be carried on in a continuous step-by-step operation. More particularly the present process relates to the formation of irregular shapes from high carbon steel or other alloys into the finished desired cross-section with all of the steps being carried out while the metal is cold.

The present invention is of utility in the formation of cross-sections Which may be utilized for such purposes as structural members, cutting tools and the like. Some shapes are formed from separate pieces which are welded together and are then ground or machined to the finished configuration. The process of extrusion is normally used with softer materials. According to the present invention a method is utilized which enables cross sections to be produced from strip material such as high carbon steels and the like by a series of cold forming steps which includes blanking, upsetting, splitting, coining and die forming including bending. With the present invention, material waste from such extra and costly operations as grinding is practically eliminated. Manufacturing time and labor are reduced to a minimum since the finished item results from deformation of the original precision (close tolerance) strip stock without the necessity for such operations as welding and the like after the item has been shaped.

The primary object of the present invention is, therefore, to provide an improved process for cold forming high carbon steel and other strip steel alloys as well as other metals without the necessity of welding, grinding or other time consuming and expensive steps. By way of example and not limitation, materials, such as magnesium, aluminum and so on, used in the construction of supersonic air craft which must be held to extreme accuracy and thickness tolerances may be produced accurately and relatively cheaply with the present cold forming process.

Another object of the present invention is to provide a process of the character described which enables cross sections to be produced from strip stock in a cold condition without destroying or weakening the strength of the material and in some cases actually strengthening it.

Further objects and advantages of the present invention will be apparent from the following specifications and appended claims and from the accompanying drawings wherein:

FIG. 1 depicts the step-by-step formation of a saw chain tooth from a continuous strip;

FIGS. 2 through 7 illustrate the various metal working steps involved in the present invention;

FIG. 8 is a side elevation of the finished saw tooth; and

FIG. 9 is a rear elevation of the tooth.

Although the metal forming method according to the present invention may be utilized to produce many varied cross sections the invention as herein disclosed is illustrated and described as applied to the formation of individual teeth for use on saw chain links.

Referring to the drawings, FIG. 1 illustrates the strip stock 1 which may be composed of high carbon steel or other alloy which is capable of being blanked out or crenellated as illustrated in FIG. 1 so as to form successive tooth blanks 2. In practice the blanked strip 1 may be progressively fed or indexed longitudinally between die halves by means of the holes 3 or by any other suitable means known in the art. In the present instance, the projecting tooth blanks 2 are formed with a slanting top surface 4 which results in forming a rake angle for the finished saw tooth as will be understood by those skilled in the art. The crenellations on the strip stock 1 may be produced by blanking or any other known method.

As illustrated in FIG. 1, each tooth blank 2, after it is cut, goes through a series of six cold forming operations to form the V-shaped tooth configuration shown in FIGS. 8 and 9. FIGS. 8 and 9 show the finished saw tooth after it has been blanked, formed and then cut or punched from the strip 1 along the dotted line in FIG. 1. The six stages or steps through which each tooth blank progresses are illustrated by the six teeth, 6 to 11 in FIG. 1 and the respective operations are detailed in FIGS. 2 through 7. Except for sharpening, the fininhed tooth is formed completely by use of six punch and die stations through which each tooth blank is successively indexed. Thus the die itself is made up of two mating halves between which the strip stock is advanced longitudinally. As will be well understood by those skilled in the art, the die halves are parted, the stock advanced one station and the die halves closed and clamped and then a punch is impacted against the tooth blank within the die cavity formed by the die halves.

In FIG. 2, the strip stock 1 is shown in its clamped position between the die halves 12 and 13 which provide the first station where the original tooth blank is upset, i.e., thickened and shortened by the impact of the punch 14 on the upper surface 4 of a blank. The impact forces the blank to conform to the widened cavity portion 16 between the die halves. After the tooth blank has been upset it is in the widened and shortened form shown at 5 in FIG. 1. The upset blank is then advanced to the second station shown in FIG. 3.

FIGS. 3 through 5 illustrate a series of splitting steps or stations through which the tooth blank passes. As shown in FIG. 3, the die cavity is formed with the inclined surfaces 16 and 17 so as to allow the top portion of the upset tooth blank to be split by the punch chisel 1S and spread to begin the formation of the legs of the V of the final saw tooth. As seen in FIGS. 4 and 5, progressive splitting and spreading of the legs of the V is accomplished by the punch chisels 18 and 19 which may be identical in shape with the chisel 15 but which extend progressively deeper into their respective die cavities. The

depth of the die cavities increases from that shown in FIG. 3 to that shown in FIG. 5 to allow the upset blank to be further split and spread. It will be understood that the number of splitting steps or stations required will depend upon the particular end shape desired and the character of the material being worked. The shape of the tooth blank for the three corresponding splitting stages shown in FIGS. 3, 4 and 5 are shown at 7, 8 and 9 respectively in FIG. 1.

As will be understood by those skilled in the art, the splitting of the upset portion of the tooth blank by the chisels 15, 18 and 19 results in a sharp angle at the junction of the inside faces of the legs of the V tooth causing a potential fatigue point in the structure. As illustrated in FIG. 6, the tooth blank is subjected to a coining step wherein the intersection of the inside faces of the V is given a radius 20 by means of a coining punch 21 so as to prevent possible fatigue of the tooth along this line under working stresses. Following the coining step, a final forming operation is accomplished by the forming punch 22 in which the finished angle is given to the legs of the V shape tooth. As shown in FIGS. 8 and 9, the top and bottom edges of each leg of the V are beveled. Referring to FIG. 9, each of the legs 23 has a bevel 24 on the bottom side and a bevel 25 on the top side.

After the V portion of the tooth has been completely formed, the holes 26 and 27 may be punched in the blank 1 and the tooth stamped from the blank on the dotted line shown in FIG. 1 to form the finished product shown in FIGS. 8 and 9. After the tooth is hardened, the only remaining operation is that of the normal sharpening of the leading or cutting edge 28 of the tooth.

With the present method involving upsetting, splitting, coining and forming it will be realized that by varying the shapes of the tools or punches involved and the shapes of the die cavities, various cross sections may be fabricated from strip stock in an efficient and economical manner. Each of the six operations illustrated in FIGS. 2 through 7 may be performed simultaneously with each tooth blank 2 advancing through the series of operations as the strip is indexed longitudinally between the clamping die halves. While the various steps in the present invention have been described as being performed by punches, chisels, etc., it will be appreciated that various equivalent tools such as rollers may be used to perform these operations.

From the foregoing, it will be apparent to those skilled in the art that the present invention provides new and useful improvements in the process of cold forming metals of the character described. The details of the method steps utilized within this invention may be subjected to numerous modifications well within the purview of this invention and applicants intend only to be limited to a liberal interpretation of the specification and appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A method of forming a cross section from metal strip stock comprising: upsetting a portion of the edge of the strip by the application of pressure to thicken and foreshorten the same, and then splitting and forming by pressure said upset portion of the final configuration, all of said steps being performed while the metal is cold.

2. The method according to claim 1 wherein said edge portion is upset by an impact force to cause the metal to flow within a die cavity, said edge portion being then progressively longitudinally split into sections and simultaneously spread.

3. The method according to claim 2 wherein said splitting and spreading is accomplished by a plurality of repeated impacts by a splitting tool to deepen the split while said strip is held within a die cavity, said sections being spread by said tool to conform with said cavity.

4. The method according to claim 3 including the step of coining a radius at the intersection ofsaid sections after the splitting operations.

5. The method according to claim 4 wherein said coining step is followed by a forming step wherein the material of said sections is caused to flow by impact to conform to a die cavity to form the final configuration and the longitudinal edges thereof are beveled.

6. A method of forming a cross section from fiat strip stock comprising: upsetting the edge portion of said strip, progressively longitudinally splitting said upset portion to form sections and simultaneously spreading said sections, coining a radius between said sections, and then die forming said sections to the final desired configuration.

7. A method of forming saw chain teeth from metal strip stock comprising: blanking an edge portion of said strip to form a plurality of saw tooth blanks and indexing said strip in a manner to subject each tooth blank to the steps of; upsetting the tooth blank, progressively longitudinally splitting said upset portion to form sections and simultaneously spreading said sections, coining a radius between said sections, and then die forming said sections to final desired configuration.

8. A method of forming saw chain cutter links from metal strip stock comprising: stamping out portions of one edge of said strip to form saw tooth blanks having a desired rake angle in plan, advancing each tooth blank through a series of stations between clamping die halves having successive die cavities for first upsetting the blank by impact to thicken and foreshorten the same, then splitting the upset blank to the desired depth to form tooth sections and simultaneously spreading said sections, coining a radius between said tooth sections, then die forming the final configuration of the sections, and then stamping the chain link configuration including the formed tooth from the strip, all of said steps being performed while the metal is cold.

References Cited UNITED STATES PATENTS 2,023,633 12/1935 Lawson 72--375 2,854,866 10/1958 Mall et al 76l 12 GRANVILLE Y. CUSTER, JR., Primary Examiner. 

8. A METHOD OF FORMING SAW CHAIN CUTTER LINKS FROM METAL STRIP STOCK COMPRISING: STAMPING OUT PORTIONS OF ONE EDGE OF SAID STRIP TO FORM SAW TOOTH BLANKS HAVING A DESIRED RAKE ANGLE IN PLAN, ADVANCING EACH TOOTH BLANK THROUGH A SERIES OF STATIONS BETWEEN CLAMPING DIE HALVES HAVING SUCCESSIVE DIE CAVITIES FOR FIRST UPSETTING THE BLANK BY IMPACT TO THICKEN AND FORESHORTEN THE SAME, THEN SPLITTING THE UPSET BLANK TO THE DESIRED DEPTH TO FORM TOOTH SECTIONS AND SIMULTANEOUSLY SPREADING SAID SECTIONS, COINING A RADIUS BETWEEN SAID TOOTH SECTIONS, THEN DIE FORMING THE FINAL CONFIGURATION OF THE SECTIONS, AND THEN STAMPING THE CHAIN LINK CONFIGURATION INCLUDING THE FORMED TOOTH FROM THE STRIP, ALL OF SAID STEPS BEING PERFORMED WHILE THE METAL IS COLD. 